U.S. patent number 10,493,575 [Application Number 15/944,136] was granted by the patent office on 2019-12-03 for clamping chuck.
This patent grant is currently assigned to Erowa AG. The grantee listed for this patent is Erowa AG. Invention is credited to Hans Hediger.
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United States Patent |
10,493,575 |
Hediger |
December 3, 2019 |
Clamping chuck
Abstract
The invention relates to a clamping chuck for clamping pallets
furnished with a clamping spigot. The clamping chuck has a locating
opening for the clamping spigot and a clamping device for clamping
the clamping spigot in the locating opening. A plurality of sensors
are arranged on the clamping chuck, by means of which the clamping
force actions on the clamping spigot may be determined as well as
other values. The clamping chuck is equipped with a transmitter for
wireless transmission of parameters detected by means of the one or
more sensors.
Inventors: |
Hediger; Hans (Reinach,
CH) |
Applicant: |
Name |
City |
State |
Country |
Type |
Erowa AG |
Reinach |
N/A |
CH |
|
|
Assignee: |
Erowa AG (Reinach,
CH)
|
Family
ID: |
63852626 |
Appl.
No.: |
15/944,136 |
Filed: |
April 3, 2018 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20180304428 A1 |
Oct 25, 2018 |
|
Foreign Application Priority Data
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|
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Apr 21, 2017 [CH] |
|
|
00533/17 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23B
31/1071 (20130101); B23Q 1/0072 (20130101); B23Q
17/006 (20130101); B23Q 17/005 (20130101); Y10T
279/21 (20150115); Y10T 279/17752 (20150115) |
Current International
Class: |
B23Q
17/00 (20060101); B23Q 1/00 (20060101); B23B
31/107 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
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|
|
|
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102011080504 |
|
Feb 2013 |
|
DE |
|
2759372 |
|
Nov 2014 |
|
EP |
|
Other References
Machine translation, German Patent Document, DE102011080504 A1,
Jaeger eta l., Feb. 7, 2013. (Year: 2013). cited by
examiner.
|
Primary Examiner: Gates; Eric A.
Assistant Examiner: Su; Chwen-Wei
Attorney, Agent or Firm: Maginot, Moore & Beck, LLP
Claims
The invention claimed is:
1. A clamping chuck for clamping pallets furnished with a clamping
spigot, wherein the clamping chuck has a locating opening for the
clamping spigot and a clamping device having clamping elements for
providing a pull-in force for clamping the clamping spigot in the
locating opening, and wherein at least one sensor is arranged on
the clamping chuck, by means of which at least one parameter (a) of
the clamping chuck and/or (b) of the interaction between the pallet
and the clamping chuck and/or (c) of the pallet can be captured,
wherein the clamping chuck is equipped with a transmitter for
wireless transmission of parameters detected by the at least one
sensor, wherein said at least one sensor includes a first sensor
configured and operable to detect the pull-in force acting on the
clamping spigot.
2. The clamping chuck according to claim 1, wherein the first
sensor is configured and arranged on the clamping chuck in such
manner that elastic material deformations of the clamping chuck are
measurable when a pallet is clamped securely.
3. The clamping chuck according to claim 1, wherein said at least
one sensor further includes a second sensor configured and operable
to detect; the position of a pallet on the clamping chuck.
4. The clamping chuck according to claim 3, wherein the second
sensor is configured and arranged in the region of a top side of
the clamping chuck in such manner that the presence of a pallet on
top of it can be detected.
5. The clamping chuck according to claim 1, wherein the at least
one sensor further includes a second sensor and a third sensor
configured and operable to detect the position of an element
serving to actuate the clamping elements.
6. The clamping chuck according to claim 5, wherein the clamping
device is provided with an actuating piston which is movable
between a starting position and a locking position for actuating
the clamping elements, and wherein in the locking position the
actuating piston pushes the clamping elements radially inwards to
bear on the clamping spigot in a force-locking manner, wherein the
third sensor is arranged inside the clamping chuck in such manner
that the location of the actuating piston in the starting position
can be detected.
7. The clamping chuck according to claim 1, wherein the first
sensor includes strain gauges.
8. The clamping chuck according to claim 7, wherein the first
sensor is attached to the clamping chuck in force-locking and/or
materially bonded manner such that the signal therefrom is
essentially proportional to the clamping force.
9. The clamping chuck according to claim 1 wherein a top side of
the clamping chuck is provided with Z-supports for the pallet,
wherein the Z-supports are arranged radially outside the locating
opening, and wherein the first sensor is arranged radially between
the locating opening and a circular line which intersects the
Z-supports.
10. The clamping chuck according to claim 1, wherein, the clamping
chuck is provided with a hollow-cylindrical extension which
delimits the locating opening radially, wherein the extension is
furnished with radial bore holes), in which the clamping elements
are braced in the Z-direction in form-locking and/or in
force-locking manner.
11. The clamping chuck according to claim 1, further comprising an
actuating piston which is movable between a starting position and a
locking position for actuating the clamping elements, wherein the
actuating piston pushes the clamping elements radially inwards, so
they bear on the clamping spigot in force-locking manner, wherein
the actuating piston is displaceable into the locking position by
compression springs and displaceable pneumatically into the
starting position against the force of the springs.
12. The clamping chuck according to claim 1, wherein a
microprocessor control is integrated in the clamping chuck, the
microprocessor is configured and operable to evaluate data
collected by the at least one sensor before said data is forwarded
to the transmitter.
13. The clamping chuck according to claim 1, wherein the clamping
chuck is provided with a power supply, in the form of batteries,
for at least the transmitter and for the at least one sensor.
Description
PRIORITY CLAIM
This application claims priority to Swiss Application No. 00533/17,
entitled "CLAMPING CHUCK", filed in the name of the same inventor
and applicant on Apr. 21, 2017, the entire disclosure of which is
incorporated herein by reference.
The present invention relates to a clamping chuck.
Clamping chucks of the type under discussion here are used to clamp
pallets and/or workpiece carriers so that they are immobilised in a
defined position. In this context, the respective clamping chuck is
typically mounted securely on the machine bench of a processing
machine while the pallet can be secured immovably and repeatedly in
a precise position by the clamping chuck. While the pallet is
equipped with a clamping spigot, the clamping chuck has a locating
opening and a clamping device for clamping the clamping spigot in
the locating opening. The pallet usually carries a workpiece to be
processed or a tool.
In order to be able to use such a clamping chuck in semi- or fully
automatically running work processes, it must be possible for the
pallet to be inserted in the clamping chuck and removed from it
again by means of a handling robot. At the same time it is
important that the pallet is secured on the clamping chuck with a
minimum clamping force, and the clamping elements of the clamping
chuck must have also been completely released and unlocked again
before the pallet is removed. If the pallet is not fixed in the
clamping chuck correctly, for example, there is a risk of vibration
or even that it may become detached while the workpiece secured on
it is undergoing mechanical processing, during a milling process
for example, which can lead to considerable consequential damage.
If the workpiece carrier is to be lifted off the clamping chuck
after the processing operation, again it must be ensured that the
locking mechanism has been completely unlocked, that is to say it
is fully released, so that the workpiece carrier can be lifted off
the clamping chuck without consequential damage. Of course, lifting
a workpiece carrier off when the clamping elements are not fully
unlocked can also lead to consequential damages and considerable
costs.
A clamping device with a clamping chuck for detachable fixing of a
workpiece carrier is known from EP 2 052 808 A1. The clamping chuck
is equipped with a locking mechanism comprising a plurality of
clamping elements, which engage in a clamping spigot connected to
workpiece carrier when in the in the locking position. Each
clamping element is provided with a through hole, which is closed
off at one side when the respective clamping element is locked
correctly. In addition or alternatively thereto, an actuating
element furnished with a through hole is assigned to each clamping
element, and the through hole on the actuating element is closed
off on one side when the associated clamping element is locked
and/or unlocked correctly. The through holes of the clamping
elements and the actuating elements are connected to a pneumatic
source via a common connecting line. At least one sensor is
provided in the connecting line to capture the airflow. With the
sensor, it is possible to detect whether the clamping elements have
been unlocked, and/or locked correctly. The sensor is connected to
an electronic control and evaluation device.
Although such a clamping device has proven effective in practice,
it would be desirable if the one or more parameters/data elements
captured by a sensor could be forwarded simply to a transfer point
for collection, evaluation or further processing.
A clamping device for a machine tool is also known from EP 2 759
372 A1. The machine tool has a rotating spindle with a tool holder
for a tool. A clamping device is provided in order to clamp the
tool. The clamping device is equipped with force sensors at various
measurement points to capture the clamping forces acting at each of
the various measurement points, to detect whether the tool has been
clamped correctly or incorrectly in the tool holder. The force
sensors are arranged on an annular bearing surface of the tool
holder. The sensors project above the bearing surface in such
manner that they are pressed together when the tool is clamped. The
purpose of this is both to enable the clamping force to be captured
and to detect whether the tool has been clamped correctly or
whether a misalignment and/or incorrect positioning has occurred.
The force sensors used are surface acoustic wave (SAW) sensors. The
force sensors are arranged on the bearing surface rotationally
symmetrically about the centre axis of the machine tool. When the
tool is aligned correctly, the force sensors capture clamping
forces of equal strength, but if a tool is not clamped straight
clamping forces of different strength are captured by the force
sensors. The electrical signals of the sensors are transmitted
wirelessly to a transmitting and receiving unit and evaluated in an
evaluation unit.
Finally, EP 2 457 688 A1 discloses a method for positioning and
fixing workpieces. The presence and/or absence of workpieces or
workpiece carriers can be detected by means of process steps.
The object of the invention is to provide a clamping chuck
belonging in the technical area described in the introduction, with
which it is possible to reliably capture one or more parameters,
particularly such parameters that monitor or indicate clamping
and/or contacting and/or releasing of the pallet, and transmit them
to a receiver without the need for the presence of data lines.
The solution to this object is defined with the features of claim
1. According to the invention, the clamping chuck for clamping
pallets furnished with a clamping spigot has a locating opening for
the clamping spigot and is equipped with a clamping device having
clamping elements for clamping the clamping spigot in the locating
opening, wherein at least one sensor is arranged on the clamping
chuck, by means of which at least one parameter of the clamping
chuck and/or of the pallet and/or of the interaction between the
pallet and clamping chuck may be captured, and wherein the clamping
chuck is equipped with a transmitter for wireless transmission of
parameters detected by means of the one or more sensors.
The fact that the clamping chuck is equipped with a transmitter for
wireless transmission of parameters detected by means of the one or
more sensors means that the detected parameters can be received and
evaluated remotely from the clamping chuck without necessitating
the presence of data lines therefor. The transmitted data may be
received by a receiver and forwarded from there to any other
devices, such as for example an electronic transfer point. This is
advantageous on the one hand for the purposes of automated
workflows, in which the pallets are swapped in and out by a
handling robot, since the measurement data can be transmitted to
the robot by the transfer point in the form of control commands. On
the other hand, significant parameters such as the correct clamping
of the pallet in the clamping chuck can also be monitored and/or
evaluated continuously and optionally linked with further
parameters.
Preferred embodiments and further developments of the clamping
device are described in the dependent claims.
Thus in a preferred further development it is provided that the
clamping chuck is equipped with a first sensor, by means of which
the clamping force acting on the clamping spigot may be determined.
A qualitative statement regarding a correct clamping of the pallet
may be made on the basis of the clamping force acting on the
clamping spigot, which is advantageous for purposes of an automated
workflow and at the same time ensures increased safety.
The first sensor is preferably designed and arranged on the
clamping chuck in such manner that when a pallet is clamped elastic
material deformations of the clamping chuck are measurable. The
measurement of the elastic material deformation of the clamping
chuck represents a particularly simple option for drawing
conclusions with regard to the clamping force--i.e., the force with
which the pallet is clamped to the clamping chuck.
The clamping chuck is particularly preferably equipped with a
second sensor, by means of which the positioning of a pallet on the
clamping chuck is detectable. The detection as to whether a pallet
is positioned on the clamping chuck is again advantageous for the
purposes of automated workflow, since it may serve to issue the
release to the clamping chuck to clamp the pallet, for example.
In another preferred further development, the clamping chuck is
equipped with a third sensor, by means of which the position of an
element serving to actuate the clamping elements may be detected.
With this, it may be determined whether the clamping elements are
in the released position, which is important for purposes of
automated pallet changing, since the pallet cannot or must not be
removed until said element is no longer pressing the clamping
elements into the clamping position.
In a particularly preferred further development, the second sensor
is arranged in the area of the upper side of the clamping chuck in
such manner that the presence of a pallet above it is detectable.
This arrangement of the sensor is particularly advantageous, since
such a sensor can be mounted and designed relatively simply.
A preferred further development of the clamping chuck provides that
the clamping device thereof is equipped with an actuating piston
which is displaceable between a starting and a locking position for
actuating the clamping elements, wherein the actuating piston
pushes the clamping elements radially inwards in the locking
position, so that they bear on the clamping spigot in force locking
manner, and wherein the third sensor is arranged inside the
clamping chuck in such manner that the position of the actuating
piston is detectable in the starting position. At all events, with
the sensor it is possible to detect reliably whether the actuating
piston has been displaced into the starting position, so that the
clamping elements are also in the open position, or at least that
they can be pushed back into the open position. With a sensor it is
also relatively simple to determine a defined position of the
actuating piston, in particular the starting position thereof.
The first sensor is particularly preferably a sensor based on a
strain gauge (DMS). DMS sensors are relatively inexpensive, have
high resolution and allow very accurate measurement results.
The first sensor is attached to the clamping chuck preferably at
least in force-locking manner, particularly preferably at least in
force-locking and in bonded manner, so that its signal is
substantially proportional to the clamping force. In this way, a
statement regarding the clamping force may be made directly.
The first sensor is most particularly preferably arranged in the
radial direction between a circular line intersecting the
Z-supports for the pallet and the locating opening of the clamping
chuck. This arrangement has proved to be particularly advantageous
for purposes of high resolution and measurement accuracy.
A further particularly preferred further development provides that
the clamping chuck is furnished with a hollow-cylindrical extension
which radially delimits the locating opening, wherein the extension
is furnished with radial boreholes in which the clamping elements
are braced in form-fitting manner in the Z-direction. This design
is not only extremely sturdy and stable but it also supports an
elastic material deformation proportional to the clamping force of
the area in which the first sensor is arranged.
The actuating piston is preferably displaceable into the locking
position by means of compression springs and into the starting
position pneumatically against the force of the compression
springs. This design ensures that the pallet is and will remain
securely clamped to the clamping chuck even if the pneumatic system
fails.
In another preferred further development of the clamping chuck it
is provided that a microprocessor control is integrated in the
clamping chuck, by means of which the data collected by the sensors
is evaluated and/or processed before it is transferred to the
transmitter. This design enables the measured data to be processed
further particularly simply.
Finally, according to a preferred further development the clamping
chuck is equipped with a power supply, particularly in the form or
batteries or rechargeable batteries. This enables electrical power
to be supplied to the transmitter and the sensor(s) and any other
electrical or electronic components. In this respect, such a
clamping chuck may be operated automatically to the extent that it
does not need to be connected to a voltage source.
The following detailed description and the entirety of the patent
claims will be disclosed further advantageous embodiments and
combinations of features of the invention.
The figures of the drawings serving to explain an embodiment
show:
FIG. 1 a perspective view of the clamping chuck together with a
pallet;
FIG. 2 a view from above of the clamping chuck together with the
pallet accommodated therein;
FIG. 3 the abstracted clamping chuck in a cross section along line
A-A in FIG. 2;
FIG. 4 a simplified representation of the clamping chuck together
with the pallet lifted off in a cross section along line A-A in
FIG. 2;
FIG. 5 the abstracted clamping chuck together with the pallet
positioned thereon without clamping;
FIG. 6 the abstracted clamping chuck together with the pallet
clamped thereon;
FIG. 7 the clamping chuck together with a receiver, a gateway and a
robot.
FIG. 1 shows a perspective view of the clamping chuck 1 together
with a pallet 30. The clamping chuck 1 substantially comprises a
base plate 2 and a chuck inner part 3, while the pallet 30 is
equipped with a clamping spigot 31 for clamping in the chuck inner
part 3. The chuck inner part 3 is connected to the base plate 2 via
a plurality of fixing screws 4. The inner part 3 of the clamping
chuck 1 is provided with a locating opening 5 for the clamping
spigot 31. On its upper side 6, the chuck inner part 3 has a round
cover plate 8, on which four circular bearing surfaces 7 are
arranged, forming the Z-support for the pallet 30. The Z-supports 7
are raised above the flat top surface 6 of the chuck inner part 3.
The pallet 30 has a flat underside 32, which rests on the
Z-supports 7 when the pallet is clamped to clamping chuck 1. Each
of these Z-supports 7 has a discharge opening. In general, the X-Y
plane in such a clamping chuck 1 extends parallel to the top
side/surface 6 of the clamping chuck 1, whereas the Z-direction
extends at right angles thereto. At the same time, the Z-direction
extends parallel to the longitudinal centre line of the locating
opening 5. Centring means (not shown in greater detail) are
provided for centring the pallet 30 in the X-Y direction. In this
context, the term pallet is used representatively for any kind of
carrier on which a tool or workpiece can be secured.
A first sensor 9, represented schematically, is arranged in the
area of upper side 6 of the clamping chuck 1 and is accommodated in
a borehole created in the top cover plate 8. This first sensor 9 is
designed and connected to the clamping chuck 1 or the top cover
plate 8 thereof in such manner that elastic material deformations
of the clamping chuck 1, specifically of the top cover plate 8, may
be measured therewith. The first sensor 9 is connected to the top
cover plate 8 at least in force-locking manner, preferably in
force-locking and material-bonded, optionally also in form-locking
manner, preferably welded or adhesively bonded. The first sensor 9
is arranged radially between a circular line L which intersects the
Z-supports 7 and the locating opening 5.
A second sensor 10 with which the bearing or presence of a pallet
30 may be detected is arranged on the top side of the clamping
chuck 1. The top side of this second sensor 10 is positioned
slightly lower than the top side of the Z-supports 7, so that a
pallet 30 does not rest on the second sensor 10 when it is
deposited on the clamping chuck 1. The clamping chuck 1 also has a
third sensor, not shown in this view, which will be explained in
more detail later in this document.
The base plate 2 is furnished with a recess 24 on the side, which
serves to accommodate a transmitter 25. Batteries or rechargeable
batteries are preferably provided to supply energy to the
transmitter 25, and may preferably be fitted in a separate battery
compartment in the base plate 2, neither the batteries nor the
battery compartment being shown in detail here. Optionally, a mains
adapter or a device for converting energy from the environment
(energy harvesting) may be provided. The base plate 2 is also
furnished with lateral ports 17, through which compressed air is
fed to actuate the clamping device, in particular to open the
clamping device. The compressed air may also be used to clean
bearing surfaces by blowing them off and/or apply further clamping
force for the clamping device.
FIG. 2 shows a view from above of the clamping chuck 1 together
with the pallet 30 mounted therein. This representation serves to
show the course of cross section A-A for the following
illustrations.
FIG. 3 shows a perspective view of the clamping chuck 1 in a
cross-section along line A-A of FIG. 2. Since the construction and
operating principle of such a clamping chuck 1 are basically known,
from EP 1 344 599 A1 for example, particularly in the following
only a few or a few essential components of the clamping chuck 1
will be discussed. The central locating opening 5 of the clamping
chuck 1 is delimited by a hollow-cylindrical extension 13, which is
constructed as a single part with the cover plate 8 and extends
vertically downwards towards the bottom 2A of the base plate 2. The
clamping chuck 1 is furnished with a clamping device which consists
essentially of an actuating piston 18 that is biased by compression
springs 20, and of clamping elements in the form of clamping balls
15. The hollow-cylindrical extension 13 has radial boreholes 14 in
which the clamping balls 15 fit. The clamping balls 15 are
supported in the axial or Z-direction on the hollow-cylindrical
extension 13. The actuation of the clamping balls, i.e., the radial
displacement of the clamping balls 15 is caused by the actuating
piston 18, which is biased downwards towards the bottom 2A of the
base plate 2 by means of the compression springs 20. A pressure
chamber 21 is also arranged in base plate 2, and may be pressurised
with compressed air in order to shift the actuating piston 18
against the force of the springs 20.
This view shows that the first sensor 9 is accommodated in a bore
hole 12 which is created in the cover plate 8. In addition to the
second sensor 10, a third sensor 11 may also be seen, arranged on
the underside of the top cover plate 8 of the clamping chuck 1.
This third sensor 11 serves to detect the position of the actuating
piston 18.
The first sensor 9 is designed and connected to the clamping chuck
1 or the top cover plate 8 thereof in such manner that it may serve
to measure elastic material deformations of the clamping chuck 1,
specifically of the top cover plate 8. It may also be seen that the
first sensor 9 is arranged radially outside the locating opening 5
but inside the Z-supports 7.
The second and third sensors 10, 11 are preferably sensors that
function inductively in the form of inductive proximity switches,
by means of which the position of a pallet or of the actuating
piston 18 is detectable. The first sensor 9 is preferably a sensor
based on strain gauges, hereinafter referred to as a DMS sensor, by
means of which elastic material deformations of the clamping chuck
1 may be measured, thereby allowing qualitative statements to be
made about the clamping condition of a pallet at the clamping chuck
1, as will be explained in greater detail below. Each of the three
sensors 9, 10, 11 is connected to the transmitter 25 via an
electrical conductor L1, L2, L3, wherein said three conductors L1,
L2, L3 are only indicated schematically. The transmitter 25 serves
particularly to ensure the wireless transmission of the signals
requiring delivery at the sensors 9, 10, 11. Although for the sake
of simplicity only a transmitter is referred to in each case here,
the transmitter 25 preferably comprises a microprocessor control as
well, by means of which the sensor signals may be processed, and
optionally supplied with further information such as the battery
status for example. The processed sensor signals are transmitted
wirelessly by means of the transmitter 25.
FIG. 4 shows a cross-section along line A-A in FIG. 2 of the
clamping chuck 1 together with the pallet 30 raised off the chuck,
wherein the transmitter and the connecting lines are not
represented. To ensure that the clamping spigot 31 can be inserted
in the locating opening 5 far enough to enable it to be clamped
securely, the actuating piston 18 must have been displaced into the
raised position--the starting position--shown in FIG. 4. For this
purpose, a corresponding overpressure is built up inside the
pressure chamber 21 pneumatically. This makes it possible for the
clamping balls 15 to be pushed radially outwardly far enough to
extend into a recess 19 in the actuating piston 18 formed by a
circumferential annular groove. Even if the clamping balls 15 still
extend into the locating opening 5 when the clamping spigot 31 is
introduced, they are forced back transversely to the longitudinal
center line LM by the clamping spigot 31.
In the view according to FIG. 4, it is detected by means of the
third sensor 11 that the actuating piston 18 is in its raised
position, while the second sensor 10 detects that a pallet 30 is
not positioned on top of clamping chuck 1. Consequently, a "1"
signal exists at the third sensor 11, while a "0" signal exists the
second sensor 10. At the first sensor 9 there is a signal which is
proportional to the deformation of the clamping chuck 1. The
pending signals are transmitted wirelessly by the transmitter to a
receiver (not shown). The receiver may be part of a machine
controller, for example, via which a handling robot (not shown) is
actuated. The actual status of the clamping chuck 1 may be detected
on the basis of the signals which are pending at the three sensors
9, 10, 11 and are transmitted to the receiver. In the present case,
it is detected that the clamping chuck 1 is in the open position,
but no pallet 30 has been placed on it or clamped securely in it.
Consequently, a release to transfer a pallet 30 to the clamping
chuck 1 can be issued to the handling robot.
FIG. 5 shows a cross-section along line A-A in FIG. 2 of the
clamping chuck 1 together with the pallet 30 placed on the clamping
chuck 1 but not clamped securely therein. The pallet 30 lies
unsecured on the clamping chuck 1, which is to say under its own
dead weight and the weight of any workpiece or tool fastened to it.
The actuating piston 18 still remains in its raised position, in
which the clamping balls 15 are pushed radially outwards. As a
result, the clamping balls 15 are not yet exerting a clamping force
on the clamping spigot 31. Via the second sensor 10, it is detected
that the pallet 30 is positioned on the clamping chuck 1, while the
third sensor 11 in its turn detects that the actuating piston 18 is
in its raised position. Consequently, a "1" signal exists at both
the second sensor 10 and the third sensor 11. At the first sensor 9
there is again a signal that is proportional to the deformation of
the clamping chuck 1. When the pallet 30 rests unsecured on the
clamping chuck 1, the clamping chuck 1 does not undergo any
measurable or significant deformation, as is discernible on the
basis of the signal present at the first sensor 9. Based on the
pending signals, the release may be issued to the clamping chuck 1
to clamp the pallet 30.
FIG. 6 shows a cross-section along line A-A in FIG. 2 of the
clamping chuck 1 together with the pallet 30 clamped securely. In
order to clamp the pallet 30 securely on the clamping chuck 1, the
overpressure built up inside the pressure chambers 21 must be
dissipated. As soon as the pressure in the pressure chamber 21
falls below a certain minimum level, the actuating piston 18 is
pressed downwards under the effect of the compression springs 20.
The clamping balls 15 are pressed inwards by the actuating piston
18. The clamping balls 15 bear on a ridge of the clamping spigot
31, causing it to be drawn further into the locating opening, where
it is clamped securely. At the same time, the underside of the
pallet 30 comes to rest immovably on the Z-supports of the clamping
chuck 1. The clamping chuck 1 is deformed under the effect of the
clamping balls 15 engaging with the clamping spigot 31. Since the
outward region of the pallet 30 rests on the Z-supports, the cover
plate 8 in the middle region is pressed upwards towards the pallet
30 resting on it by the clamping balls 15 which are braced axially
against the hollow-cylindrical extension 13. Consequently, the
clamping chuck 1, or the cover plate 8 thereof is deformed
elastically, particularly the middle region thereof, which can be
measured by means of the first sensor 9. This deformation is shown
exaggerated in FIG. 6. Of course, other regions of the clamping
chuck 1 will be deformed elastically when the pallet 30 is clamped.
However, experiments have shown that the region in which the first
sensor 9 is arranged is particularly advantageously suitable for
measuring the elastic material deformation of the clamping chuck 1
and for drawing conclusions about the pull-in force. The force with
which the clamping spigot 31 is pulled downwards, i.e. into the
locating opening is referred to as clamping and pull-in force. The
elastic material deformation measured enables the pull-in force to
be determined relatively precisely. At the same time, a statement
can also be made as to whether the pallet 30 is clamped on clamping
chuck 1 correctly and with sufficient clamping force. At all
events, the first sensor 9 delivers an output signal which is at
least approximately proportional to the clamping force. Experiments
in this regard have shown that the clamping force is calculated
with an accuracy in the order of 0.3 kN for a clamping force in the
order of 15 kN. Of course, the clamping force depends on the
structure and size of the clamping chuck. With large clamping
chucks the clamping force may easily reach a value several times
greater than the 15 kN indicated, while correspondingly lower
clamping forces are generated with smaller chucks. Regardless of
the clamping force, however, high resolutions are achievable with a
DMS sensor of the type described, so that ultimately the absolute
clamping force cam be determined with high resolution and
accuracy.
FIG. 7 is a schematic representation of the clamping chuck 1
according to the invention together with individual
elements/components of a manufacturing system. Besides the clamping
chuck 1, a receiver 26, a gateway 27 and a handling robot 28 are
illustrated, wherein the individual elements are not represented
true to scale. The generally known and commonly used technical term
gateway is used to refer to a transfer point as a switching device,
particularly a switching device in computer networks. The gripper
of the handling robot 28 holds a schematically illustrated pallet
30.
The transmitter 25 installed in the clamping chuck 1 transmits the
measurement data and the measurement values pending at the sensors
to the receiver 26, as is indicated by the schematically drawn
radio waves. The receiver 26 forwards the received data to the
gateway 27. The gateway 27 is in turn connected to the handling
robot 28. The gateway 27 receives the data processed by the
microprocessor control of the transmitter 25, such as chuck open,
no pallet present, pallet in position, pallet clamped, pallet
clamped with 10 kN, etc. Based on the transmitted, data, the
gateway 27 is able to deliver a command to the handling robot 28,
such as transfer pallet 30 to the clamping chuck 1 or remove pallet
from the clamping chuck 1, as is indicated by the line X with
arrows.
If the pallet is not clamped securely in clamping chuck 1 with a
minimum clamping force, an error message may be output by the
transmitter 25. Alternatively, the gateway 27 may detect that the
minimum clamping force has not been reached and output an error
message and/or initiate appropriate measures.
Of course, FIG. 7 shows only one exemplary configuration. For
example, a clamping chuck according to the invention may be
integrated in practically any production line and networked with
other components such as a control system or a workpiece
store--warehouse--or directly with the processing machine.
Depending on requirements, the calculated signals may also be
linked to each other to enable a decision to be reached. For
example, if it is detected that a pallet is in position but not
securely clamped, the release to clamp may be issued to the
clamping chuck for example. On the other hand, the release to the
handling robot for removing the pallet from the clamping chuck may
be withheld until a pallet is located on the chuck but no longer
securely clamped.
At all events, a clamping chuck designed according to the invention
offers an enormous variety of capabilities. Thus, in addition to
the measurement data described previously, additional data may also
be calculated by providing additional sensors, for example. For
example, an additional sensor might be provided by means of which
processing data stored on the pallet is read in and transmitted. A
sensor for determining the shape and/or size of the pallet might
also be provided, which might be particularly helpful for large
clamping systems with multiple clamping chucks. The data obtained
may also be evaluated in very many different ways, for example by
determining the number of clamping operations for the respective
clamping chuck, a change in the clamping force, particularly a
clamping force which diminishes over time, etc. Standard,
commercially available proximity switches with mechanical-,
inductive-, capacitive-, optical-, ultrasonic-, or magnetic-based
operating modes might be used for the second and third sensors for
example. Alternatively, a piezoelectric sensor might also be used
for the first sensor.
The pallet might optionally be equipped with a chip or similar that
can be read out via the clamping chuck and on which processing
data, identification codes etc. is/are stored.
For data transmission, a standardised interface such as Bluetooth
is used for preference. One of the advantages of a standardised
interface such as Bluetooth is that the data transmitted can also
be received and processed further and/or forwarded without
difficulty using other receivers such as a mobile phone, a PDA or a
computer, for example.
Of course, the embodiment described in the foregoing text is not to
be considered exhaustive or comprehensive. Thus, the sensor might
also be arranged at another location to measure the pull-in force
for example. It is only important for the sensor for measuring
clamping force that it be placed at a location that is deformed
elastically when the clamping spigot is firmly clamped. Additional
sensors may also be provided on or in the clamping chuck top
monitor further parameters. For example, an acceleration sensor
might be attached, with which the clamping chuck might be monitored
for the impacts/vibration to which it is exposed while a workpiece
is being processed. The provision of a temperature sensor is also
entirely conceivable. The data from the further sensors might also
be transmitted wirelessly via the transmitter.
On the other hand, "simpler" variants of the clamping chuck
designed according to the invention are also entirely conceivable,
with which for example only the clamping force is monitored,
wherein it is not absolutely imperative to capture the clamping
force with a high degree of resolution, but wherein it might be
sufficient to capture and/or monitor the clamping force in levels,
for example in two to ten levels, and to transmit it via the
transmitter. Moreover, variants of the clamping chucks are also
conceivable in which only two parameters are captured. Thus,
application cases are conceivable in which for example the clamping
force is captured and/or monitored and the presence of a pallet on
the chuck may also be captured. Instead of the provision of four
circular Z-support surfaces, of course it might also be possible to
provide three or more than four bearing surfaces, wherein the
bearing surfaces also do not have to be circular, but might be of
oval design instead.
Some advantages of the clamping chuck designed according to the
invention are summarised briefly below: Various parameters of the
interaction between the pallet and the clamping chuck and/or of the
clamping chuck itself and possibly of the pallet may be monitored
and transmitted wirelessly to a remote location; The transmitted
data may be captured, stored, and evaluated externally; The
parameters may be monitored continuously; The measurement of
certain parameters increases process safety, wherein particularly
continuous monitoring of the pull-in force allows access to new
capabilities in this area; It may be detected whether a pallet has
been deposited on the clamping chuck or not; It may be detected
whether the clamping device or the element serving to actuate the
clamping elements has been locked correctly; Productivity can be
increased by monitoring certain parameters; The risk of damaging
the clamping chuck is reduced; Changes in the clamping chuck over
time may be detected; The clamping chuck can be integrated easily
in an automatic manufacturing system; The entire sensor system is
arranged on the clamping chuck, so that the pallets can be produced
relatively simply and inexpensively. Thus the pallets are
backwardly compatible, i.e. existing and older pallets--workpiece
carriers--can also be used together with a clamping chuck designed
according to the invention.
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